R packages：phyloseq（二） 16s 扩增子抽平或重采样

1.导入文件

library("phyloseq")
help(package="phyloseq")
library("ggplot2")
library("ggpubr")#用于事后检验标记
qiimedata <- import_qiime(otufilename = "otu_table.tsv", 
                          mapfilename = "metadata.txt",
                          treefilename = "tree.nwk",
                          refseqfilename ="aligned-dna-sequences.fasta")

2. 查看所有样本总序列数

sample_sums(qiimedata)
#SRR10097305 SRR10097306 SRR10097307 SRR10097308 SRR10097309 SRR10097310 SRR10097311 SRR10097312 
#      14093       14084       10680       12389       17451        6992       15308       12294 
#SRR10097313 SRR10097314 SRR10097315 SRR10097316 SRR10097317 SRR10097318 SRR10097319 SRR10097320 
#      12272       18391       17311       15918       16400       13078       13108       10339 
#SRR10097321 SRR10097323 SRR10097324 SRR10097325 SRR10097326 SRR10097327 SRR10097328 SRR10097329 
#      12959        7874        8725        9194       11842       10178        9095       10673

3.抽平

set.seed(1234)#设置一个随机种子便于重复
rare.data <-  rarefy_even_depth(sub_qiimedata,replace = TRUE)
ps.rarefied <-  rarefy_even_depth(qiimedata, rngseed=1, sample.size=0.95*min(sample_sums(qiimedata)), replace=F)
#...
#114OTUs were removed because they are no longer 
#present in any sample after random subsampling
#...

其结果是按照序列数最少的样品重采样，

sample_sums(rare.data)
#SRR10097305 SRR10097306 SRR10097307 SRR10097308 SRR10097309 
#       6977        6977        6977        6977        6977 
#SRR10097310 SRR10097311 SRR10097312 SRR10097313 SRR10097314 
#       6977        6977        6977        6977        6977 
#SRR10097315 SRR10097316 SRR10097317 SRR10097318 SRR10097319 
#       6977        6977        6977        6977        6977 
#SRR10097320 SRR10097321 SRR10097323 SRR10097324 SRR10097325 
#      6977        6977        6977        6977        6977 
#SRR10097326 SRR10097327 SRR10097328 SRR10097329 SRR10097330 
#       6977        6977        6977        6977        6977

114个OTU由于重采样丰度较低而被删除。

a=qiimedata@otu_table[setdiff(rownames(qiimedata@otu_table),rownames(rare.otu)),]
#OTU Table:          [114 taxa and 25 samples]
#                     taxa are rows
#                                 SRR10097305 SRR10097306 SRR10097307 SRR10097308 SRR10097309
#fc1b43bf2d8af4dd093b78f20fe5b133           0           0           0           0           0
#74cb8df8fd0e39cfd2a0e1fdb5fc7f86           0           0           0           0           0
#e387a97e6247e0fff825ad9f1adf83ae           0           0           0           0           0

max(rowSums(a))
#[1] 13

即把序列数少于等于13的otu删除。
作图

plot_bar(rare.data, fill="Phylum")

Rplot08.png

转化OTUcount数为相对丰度

GPr  = transform_sample_counts(rare.data, function(x) x / sum(x) *100)
plot_bar(GPr, fill="Phylum")+
  facet_wrap(~group,scales = "free")

Rplot09.png

最后编辑于：2021.07.18 16:36:39

禁止转载，如需转载请通过简信或评论联系作者。